In vitro transport studies across cells grown on culture inserts are widely used for evaluating pharmacokinetic characteristics such as intestinal membrane permeability. However, measurements of the apparent permeability coefficient of highly lipophilic compounds are often limited by transport across the membrane filters, not by transport across the cultured cells. To overcome this concern, we have investigated the utility of a high-porosity membrane honeycomb film (HCF) for transcellular transport studies. Using the HCF inserts, the apparent permeability coefficient (P app ) of the drugs tested in LLC-PK1 and Caco-2 cells tended to increase with an increase in lipophilicity, reaching a maximum P app value at Log D higher than 2. In contrast, using the commercially available Track-Etched membrane (TEM) inserts, a maximum value was observed at Log D higher than 1. The basolateral to apical transport permeability P app(BL→AP) of rhodamine 123 across LLC-PK1 cells that express P-glycoprotein (P-gp) cultured on HCF inserts and TEM inserts was 2.33 and 2.39 times higher than the reverse directional P app(AP→BL) permeability, respectively. The efflux ratio (P app(B-A) / P app(A-B) ) of rhodamine 123 in LLC-PK1 expressing P-gp cells using HCF inserts was comparable to that obtained using TEM inserts, whereas the transported amount in both directions was significantly higher when using the HCF inserts. Accordingly, due to the higher permeability and high porosity of HCF membranes, it is expected that transcellular transport of high lipophilic as well as hydrophilic compounds and substrate recognition of transporters can be evaluated more accurately by using HCF inserts.

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In vitro vascular wall bilayer models for drug testing and disease modeling must emulate the physical and biological properties of healthy vascular tissue and its endothelial barrier function. Both endothelial cell (EC)‐vascular smooth muscle cell (SMC) interaction across the internal elastic lamina (IEL) and blood vessel stiffness impact endothelial barrier integrity. Polymeric porous track‐etched membranes (TEM) typically represent the IEL in laboratory vascular bilayer models. However, TEM stiffness exceeds that of diseased blood vessels, and the membrane pore architecture limits EC‐SMC interaction. The mechanical properties of compliant honeycomb film (HCF) membranes better simulate the Young's modulus of healthy blood vessels, and HCFs are thinner (4 vs. 10 μm) and more porous (57 vs. 6.5%) than TEMs. We compared endothelial barrier integrity in vascular wall bilayer models with human ECs and SMCs statically cultured on opposite sides of HCFs and TEMs (5 μm pores) for up to 12 days. Highly segregated localization of tight junction (ZO‐1) and adherens junction (VE‐cadherin) proteins and quiescent F‐actin cytoskeletons demonstrated superior and earlier maturation of interendothelial junctions. Quantifying barrier integrity based on transendothelial electrical resistance (TEER), membranes showed only minor but significant TEER differences despite enhanced junctional protein localization on HCF. Elongated ECs on HCF likely experienced greater paracellular diffusion than blocky ECs on TEM. Also, larger populations of plaques of connexin 43 subunit‐containing gap junctions suggested enhanced EC‐SMC communication across the more porous, thinner HCF. Compared with standard TEMs, engineered vascular wall bilayers cultured on HCFs better replicate physiologic endothelial barrier integrity.

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